can/does global transaction span multiple threads?

Question

We are using JTA to manage global transactions in servlet context. Additionally, some of the servlet threads are invoking asynchronous beans. Currently, I have designed it in a way so that the asynchronous bean (Work Manager) gets its own transaction.

It's my understanding that two threads can participate in the same XA transaction. But if I start using the transaction created by the servlet, for the asynchronous bean, will that block the servlet thread until all participant have committed or rolled back? Both the servlet and the async bean can commit and rollback.

The app server is WebSphere, and we are NOT using Spring.

Your response is appreciated.

Answer 1

Using the same transaction both for the servlet thread and an asynchronous worker conflicts somehow with the general idea of messaging. Messaging is a means to decouple, whereas a transaction keeps things tightly together.

In other words, if you want a worker to use the same transaction, I would not implement the worker in an asynchronous way.

As for two threads participating in the same XA transaction, this might not be supported, look here for details. Even if it worked, it could be troublesome to share resources over a thread context generally speaking (file handles, connections, transactions whatever).

As for the servlet thread, whether it blocks: I have never tried it (for the above reasons), but I assume that it does not block: You would have to wait/poll for your async workers, until they have finished (or failed). Otherwise the servlet just reaches your commit statement.